When a surgeon is accessing a region to be repaired such as the disc space between adjacent vertebrae, great care must be taken to avoid injury to the exposed nerve root. Endoscopic portal devices provide a means through which the surgeon can observe the tissue in the unobstructed path of the endoscope portal opening. In this way, the surgeon can maneuver the device to see the surgical site.
Minimally invasive spine surgery is an endoscopic procedure that uses specialized video cameras and instruments that are passed through small incisions (less than 2 cm) in the back, chest or abdomen to access the spine and perform the needed surgery.
Most types of minimally invasive surgery rely on a thin telescope-like instrument, called an endoscope, or on a portable X-ray machine, called a fluoroscope, to guide the surgeon while he or she is working. The endoscope is inserted through small incisions in the body. The endoscope is attached to a tiny video camera—smaller than a dime—which projects an internal view of the patient's body onto television screens in the operating room. Small surgical instruments are passed through one or more half-inch incisions, which are later closed with sutures and covered with surgical tape. The fluoroscope is positioned around the patient to give the surgeon the best X-ray views from which to see the anatomy of the spine.
As with any surgical procedure, including minimally invasive spine surgery, there are general risks and procedure-specific risks. The more common general risks of spine surgery include the risk of adverse reactions to the anesthetic, post-operative pneumonia, blood clots in the legs (deep vein thrombosis) that may travel to the lungs (pulmonary embolus), infection at the site of surgery and blood loss during surgery requiring a transfusion. The specific risks of spine surgery include the risk of injury to the nerves or spinal cord resulting in pain or even paralysis, (the estimated risk of paralysis for major spinal reconstructions is somewhere around 1 in 10,000), the instrumentation, if used, breaking, dislodging or irritating the surrounding tissues, and pain from the surgery itself. On rare occasions, during a minimally invasive procedure, the planned surgery cannot be completed and requires either a second trip to the operating room or a conversion from the minimally invasive technique to a full open technique.
Endoscopic spine surgery utilizes dilation technology to create the surgical access through the soft tissue (including skin, subcutaneous fat and muscle/fascia) instead of cutting, in order to minimize access trauma. Beyond the reduced access trauma, the main difference between the endoscopic and the microsurgical microscopic techniques are 2-dimensional versus 3-dimensional vision and an angulated, close-up perspective versus a straight but remote optical perspective.
A number of instrument sets for endoscopic spine surgery are available on the market and they vary considerably in their technical specifications as well as in the indications they are designed for.
It is each individual surgeon's responsibility to ascertain that she or he is using an instrument set that is well suited for the procedure that is being planned. While an endoscopic approach to the spine reduces the (visible) trauma of the surgical approach, this minimal invasiveness comes at a price—reduced and two-dimensional visibility in and limited expandability of the surgical field. The approach and the trajectory chosen in combination with the local anatomy to a large extent define the entry into the spinal canal or the foramen. These anatomical limitations are mostly caused by osseous structures such as the facet joints, the pedicles and the laminae, but also by the exiting nerve root for foraminal approaches and the vertebral arteries for cervical approaches. Together with the characteristics of the optical system (angle of view, magnification, etc.), the size of the working channel and the tools available, this imparts clear limitations as to which places can be viewed and which lesions can be treated safely.
There are burrs, trephines and rongeurs available that allow for the endoscopic resection of bone in order to expand the operative field and to enlarge access.
However, whenever repositioning of instruments through additional access portals, blind reaming with trephines and excessive bony resection is necessary, the advantages of the minimally invasive procedure over a traditional microsurgical approach are reduced and in some cases may even turn into a disadvantage.
A clear surgical strategy and precise targeting are therefore essential. Biplanar fluoroscopy for accurate planning of the approach and for intraoperative control and documentation of instrument position is a prerequisite. When, as it is often the case, tissue modulation technologies such as laser and radiofrequency bipolar devices are utilized in endoscopic spinal surgery, these devices and their potential complications need to be fully understood.
Because of that, there is less interference with the facet joint than with the posterolateral approach, but short pedicles and a large bulging disc can still make the access to the ventral epidural space difficult.
Endoscopic approaches to the cervical spine include, but are not limited to anterior approach and posterior approach.
While traditional microsurgery requires a discectomy, traversing the disc space with an endoscope requires the resection of only a small amount of disc tissue. Sequestrectomy and when required removal of osteophytes is achieved by using a wide range of special instruments including burrs, trephines, microresectors, various types of forceps, drills, hooks and bipolar microelectrodes.
By means of this approach, the foraminal areas and the spinal canal, but not the interpedicular space can be reached with excellent control of the operating field.
More so than in the other segments of the spine, the anterior endoscopic approach facilitates the effective anatomical decompression of the spinal canal and/or the nerve roots (plus in select cases even the vertebral artery) without the requirement to replace the disc by means of a fusion or an arthroplasty. In general, there is no need for a drain or for postoperative immobilization.
The posterior approach is very similar to the traditional microscopic-assisted “keyhole-foraminotomy” approach, just that it is performed using endoscopic equipment and through a smaller approach.
Indications are predominantly lateral soft disc herniations with radicular symptoms, most of which can be addressed with this technique. However, adequate experience in endoscopy and bone resection with drills is necessary due to the risks and consequences of damaging the central nervous system.
After insertion of the working sheath and the endoscope, preparation of the medial aspect of the facet joint and of the ligamentum flavum is performed to clearly identify the anatomical landmarks.
The foraminotomy is begun by bone resection at the medial aspect of the facet joint, resection of the lateral ligamentum flavum.
Then, the lateral edge of the spinal cord and the branching spinal nerve are identified.
Bone resection is necessary in nearly all cases and is performed under direct visual control using drills and bone punches, inserted through the endoscope's working channel.
Bipolar radiofrequency coagulation of the epidural venous plexus and preparation of the spinal nerve under particular attention to possibly separate motor and sensory fascicles comes next.
Depending on the pathology in the individual case, the foraminotomy can be extended towards lateral or cranio-caudal.
At the ends of the procedure, direct closure of the skin is done and no drain is required.
While recent studies have shown that endoscopic spinal surgery can be performed with lower complication rates than microsurgical spine surgery, the complications of minimally invasive spine surgery are not necessarily “minimal” when they do occur. Also, the learning curve for endoscopic spinal surgery tends to be flatter and longer than for traditional approaches.
Dural tears, nerve root damage, bleeding and infection, operating on the wrong level or on the wrong side are as real with endoscopic techniques as they are with open techniques.
With thoracic approaches, pneumothorax is also a possibility.
In addition, some injuries may be underestimated or even go unnoticed, such as a dural tear under the low-pressure irrigation of an endoscopic system.
It is an objective of the present invention to further minimize the potential for such complications by providing a unique endoscopic portal made in accordance to the invention as disclosed herein.